1. Field of Invention
The present invention relates to the oligomerization of olefins with a supported nickel catalyst, particularly a promoted nickel-zeolite catalyst.
More particularly, the present invention relates to the formation of 1-butene by reacting ethylene in the presence of this nickel-zeolite catalyst.
The present invention further relates to a novel heterogeneous nickel-zeolite catalyst.
2. Description of the Prior Art
A variety of oligomerization catalysts are currently known. These include both homogeneous and heterogeneous catalysts. In particular nickel compounds have been used to catalyze the oligomerization of lower olefins to olefinic products of higher molecular weight, e.g., dimmers, trimers, tetramers or the like.
The selectivity towards particular products and the overall reactivity depend to a large extent upon the catalyst used as well as reaction conditions. Barnett U.S. Pat. No. 3,532,765 discloses an ethylene oligomerization process using cyclopentenyl(cyclopentadienyl) nickel supported on an inorganic oxide support. This catalyst exhibits a relatively low reactivity. Barnett U.S. Pat. No. 3,134,824 discloses bis (cyclopentadienyl) nickel deposited on a support such as silica, alumina, titania, zirconia, thoria, boria, and mixtures thereof. This catalyst exhibits a relatively low selectivity for 1-butene and an overall low reactivity.
Walker, et al, U.S. Pat. No. 3,134,824, describe a process using nickelocene [bis (.eta..sup.5 -cyclopentadienyl) nickel] supported on silica-alumina as a catalyst for oligomerization of olefins. However, this catalyst is not selective nor is it active at temperatures below one hundred degrees Centigrade.
Other catalysts are disclosed in Beach et al U.S. Pat. Nos. 4,272,406, 4,272,407 and 4,293,725. The patents disclose tris(cyclopentadienyl) trinickel dicarbonyl catalysts. These catalysts exhibit a relatively low selectivity toward 1-butene relative to other C-4 compounds specifically in the range of 11-44% 1-butene, and further produce considerable quantities of higher molecular weight oligomers, e.g., hexenes, octenes, etc.
A nickel II salt derived from phosphinoacetate is currently used as a homogeneous catalyst for oligomerization of olefins. This produces a relatively high proportion of higher molecular weight olefins. In fact the product distribution of C.sub.6 -C.sub.20 olefins is relatively flat.
Triethylaluminum is also used as an oligomerization catalyst. The product distribution of C.sub.4 -C.sub.8 and higher olefins is weighted towards lower molecular weight olefins.
A particularly desirable product is 1-butene. It can be used in the formation of poly 1-butene a very useful polymer. However, the known oligomerization catalysts are unsuitable for production of a very high concentration of 1-butene from ethylene.